1. Field of the Invention
The present invention relates to an air drying apparatus and, more particularly, to an apparatus for removing moisture from an aqueous slurry. Specifically, the invention is directed at an apparatus for the drying of a reconstituted tobacco slurry in a relatively rapid and uniform manner.
2. Discussion of the Prior Art
Currently employed processes and apparatuses for the drying of aqueous slurries, such as reconstituted tobacco slurries, utilize expensive and cumbersome air hoods, chambers and duct work which are positioned above and about a tobacco sheet forming band. The drying apparatuses distribute, collect and convey the air which is required for the removal of the water vapor from the surface of the slurry. Heretofore, these hood, chamber and ducting structures have been necessary to ensure extremely uniform drying rates of high quality reconstituted tobacco products, such as cigar wrappers and binders. These processes and apparatuses, however, have proven themselves to be so complex in construction as not to be cost effective.
Among apparatuses of this type there is one in which a heating medium, such as steam, is dispensed below an endless belt conveying an aqueous slurry so as to cause water to evaporate from the slurry. An air flow is effected across the slurry which will entrain the evaporated slurry water and remove it from the apparatus. This earlier apparatus necessitates the use of complex and bulky hoods and conduits, rendering it difficult to monitor the uniformity of drying of the slurry.
Also known in the art are various types of heating and air drying apparatuses in which heat and/or an air jet is applied to an aqueous slurry or web so as to evaporate and remove moisture therefrom. Among such prior art publications are U.S. Pat. Nos. 3,228,113 to Fannon, Jr.; 1,373,396 to Andrews; 3,417,484 to McCarthy; and 3,590,493 to Gretz. None of these earlier patents disclose a fully satisfactory method or apparatus for the rapid and uniform removal of moisture from an aqueous slurry to a degree necessitated for a reconstituted tobacco slurry.
Further known is an air drying apparatus in which a slurry of reconstituted tobacco is conveyed on a foraminous belt which will allow moisture from the slurry to seep through the belt. This, in essence, will result in an impermissible loss of nicotine from the slurry, necessitating the separation of the nicotine from the removed moisture, and replacing the nicotine in the dried tobacco product.
It is of importance in the drying of slurries, particularly as applied to reconstituted tobacco slurries that, in order to obtain a high quality tobacco product, there be effected a rapid and uniform drying of the slurry through the utilization of an apparatus which will provide the desired results heretofore unattainable in the prior art while being so cost effective and economical as to be competitive in the marketplace.